1. Field of the Invention
The present invention relates to a magnetic tape and to a method of manufacturing the same. More particularly, the present invention relates to a high-density recording magnetic tape with good electromagnetic characteristics, and to a manufacturing method that permits the manufacturing of such a magnetic tape with high productivity.
2. Discussion of the Background
In recent years, as microcomputers, personal computers, and office computers such as work stations have become increasingly widespread, considerable research has been conducted into external storage media in the form of magnetic tapes for recording computer data (known as “backup tapes”).
Products in the form of data backup tapes with high recording capacity have been developed in response to an increase in the diversity and quantity of information being recorded. To achieve tapes of high recording capacity, the spacing between the magnetic layer and the magnetic head should be reduced. For example, when large protrusions and indentations are present on the surface of the magnetic layer, output drops due to spacing loss, resulting in compromised electromagnetic characteristics such as heightened dropout, an increased error rate, and a drop in the S/N. Accordingly, the magnetic recording layer surface of a data backup tape of high recording capacity is required to be extremely smooth to achieve good electromagnetic characteristics.
For example, as described in Japanese Patent No. 3,698,540, which is expressly incorporated herein by reference in its entirety, the use of a nonmagnetic layer in the form of a radiation-cured layer positioned beneath the magnetic layer is a known means of increasing the surface smoothness of the magnetic layer. Japanese Unexamined Patent Publication (KOKAI) No. 2002-42327, which is expressly incorporated herein by reference in its entirety, proposes utilizing a prescribed relation between the nonmagnetic powder, carbon black, and binder in the nonmagnetic layer while separately specifying the ultrafine hardness of the nonmagnetic layer before and after curing in the course of manufacturing a magnetic recording medium by the step of forming a magnetic layer on a nonmagnetic layer that has been formed by drying, calendering, and curing a nonmagnetic layer coating liquid. Japanese Unexamined Patent Publication (KOKAI) No. 2002-42327 describes that the above step yields a magnetic recording medium with good smoothness.
In magnetic tapes, the thickness of the tape should be reduced to achieve high recording capacity. The trend is to reduce the thickness of the nonmagnetic layer as well as the magnetic layer. Accordingly, the present inventors examined means of achieving the good electromagnetic characteristics required of high recording capacity data backup tapes in magnetic tapes having thin nonmagnetic layers. This resulted in the determination that it was difficult to obtain a magnetic tape with adequate electromagnetic characteristics with the existing art, including the methods described in Japanese Patent No. 3,698,540 and Japanese Unexamined Patent Publication (KOKAI) No. 2002-42327.